English in the trenches—those pesky compound sentences

When I started writing for kids, I relied heavily on the English I had absorbed during my school days. Unfortunately, I was a little hazy on compound sentences and their punctuation. I could see this was something of a frustration to my ICL instructor when I took the class. She tried to help, but alas, it wasn't until I started teaching that the light went on for good.

1. How do you know when you have written a compound sentence?

This is easy. If you believe you have written a compound sentence, put your finger over the conjunction which is between the alleged independent clauses and read them separately. I've highlighting the conjunction in blue in my example.

Bob has booby-trapped Fred's locker, and he is waiting in the shadows. 

I put my finger over the conjunction. (I'll wipe away the smudge on my laptop later.) Now I have the following:

Bob has booby-trapped Fred's locker.
He is waiting in the shadows.

We most definitely have two independent clauses here. Each one can be a sentence all by itself. Each has a subject and a predicate. Each sounds complete. If English was algebra, my formula for this sentence would be S / V + S / V. Let's look at another possibility. What if I had written this instead?

Bob has booby-trapped Fred's locker and is waiting in the shadows.

Now what happens when I put my finger over the conjunction?

Bob has booby-trapped Fred's locker.
Is waiting in the shadows. (Oops! There is no subject here. We're using a conjunction, but we're using it to join two verbs rather than two sentences.)

We have two parts, but only one of the parts has a subject and a predicate and sounds complete. It's actually only a simple sentence with a compound verb. The formula for this sentence would be S / V + V. You'll also notice the conspicuous absence of a comma right before the conjunction.

2. What about commas? Where do they go?

Fred approached the locker, and he spun his combination lock. 

This is a compound sentence. Notice that there is a comma at the end of the independent clause before the conjunction and the next independent clause. This is important. Although there are a couple of exceptions to using the comma, you are always safe using a comma followed by a conjunction to join compound sentences.

But, you wonder, what do you mean about those exceptions? It is appropriate to omit the comma when you join two clauses which are very short and closely related.

Fred opened his locker and Bob snickered.

No comma, but that's okay. The two clauses are closely related and are also short, so they fit the requirements for a no-comma compound sentence.

You may also, on rare occasions, use a semicolon instead of a comma. This is done when the clauses are quite long and already have commas in them being used for other purposes. I've never run across these sentences except in text books, so I find it better to just write two separate sentences.

Bob knew it was prudent to duck, run, and hide; but he wanted to see the spring-loaded cream pie hit Fred in the face. 

3. Is there anything else I should know?

Unfortunately, yes. This post is my way of giving back after having driven my ICL instructor half nuts with my compound sentence density. At least now you'll be able to hold your head up confidently, knowing you have written a sentence that is, in fact, everything a compound sentence should be by definition. For finer points, I suggest The Elements of Style. It's short. If you are a writer, buy it and read it cover to cover. (If you need a cure for insomnia and want to become an expert on the stickier points of grammar, improve yourself by wading through the Chicago Manual of Style, which is updated every ten years or so.)

See previous post for more on sentences.